Purpose: Past epidemiological studies demonstrated a nearly fivefold lower incidence of slipped capital femoral epiphysis (SCFE) in New Mexico compared with Connecticut. A recent study demonstrated some regional variability but did not address this earlier finding. We sought to reexamine the incidence of SCFE in New Mexico to improve the understanding of the epidemiology and ultimately the disorder itself.
Methods: The discharge databases for the 11 major medical centers in the state were reviewed for the ICD-9 code for SCFE (732.2) for 1995 to 2006. The data were analyzed by comparison with the 2000 New Mexico census data. The incidence data are reported as cases per 100,000 boys aged 10 to 17 years and girls aged 8 to 15 years, as per Kelsey's original article.
Results: The incidence of SCFE in New Mexico for the study period was 5.99. This is a doubling of the reported incidence in the 1960s (2.13) and represents a statistically significant change (P < 0.001). More detailed analysis of our data demonstrated a statistically significant increase during 3-year intervals: 1995-1997, 2.27; 1998-2000, 2.75; 2001-2003, 4.73; and 2004-2006, 7.38. The mean age of onset was 12.2 years. There was a male to female ratio of incidence of 1.94:1. Relative frequencies by race were as follows: 4.63x for African Americans, 2.20x for Hispanics, and 2.20x for Native Americans. A preponderance of cases was treated at the state's only tertiary pediatric orthopaedic center: 168 to 15 in the remaining 10 centers.
Conclusions: The incidence of SCFE has increased dramatically in New Mexico since Kelsey's epidemiological study in 1970. Obesity is a patient factor that has changed over this same period. According to the National Health and Nutrition Examination Survey Data for 2003/2004, the rates of obesity have tripled since 1971. In New Mexico, 25% of high-school children are estimated to be overweight. However, according to a recent study examining a national database (compiled from 27 states), the national incidence of SCFE remained fairly constant at 10.8 per 100,000.Interestingly, as more patients are seen at a tertiary center for children's orthopaedics, the rate of diagnosis in New Mexico has risen to resemble national trends. In the 1960, that center was located in a remote site and did not provide acute care for children's musculoskeletal issues. Increased obesity in children and improved access to pediatric orthopaedic evaluation may have contributed to a significant increase in reported incidence of SCFE in New Mexico.